Conventionally, a bus-bar module has been used widely as one of connecting circuits for electric parts. In the bus-bar module, a plurality of bus-bars that are formed by punching out of or bending a flat plate conductor are laid out on an insulated substrate. In using the bus-bar module, a fuse is connected to the bus-bar module to prevent a current out of rating from flowing to the bus-bar module, ensuring the safety. As this occurs, the fuse is held in a prescribed holding member (hereinafter, referred to as a fuse holder), and a cover member (hereinafter, referred to as a fuse cover) is assembled to the fuse holder for insulation. In assembling the fuse cover to the fuse holder, they are fixed to each other so as to be assembled together in such a way as not to be disassembled easily. Patent Document 1 discloses an example of a fixing structure like this.
In the fixing structure disclosed in Patent Document 1, a locking projection and an elastic locking arm are fastened together. In this case, the locking projection is provided on one of the two constituent box members that are assembled together and the elastic locking arm is provided on the other. In fixing the box members together, the elastic locking arm is moved in a fixing direction (that is, an assembling direction of the constituent box members). This causes a distal locking portion that is provided at a distal end of the elastic locking arm so as to project therefrom to strike the locking projection. Then, the elastic locking arm is elastically deflected and deformed to ride over the locking projection. Then, when the distal locking portion moves to a position where the distal locking portion rides over the locking projection completely, the elastic locking arm is deflected back to be restored, whereby the distal locking portion is locked to the locking projection.
In this fixing structure, however, the locking holding force only depends on the elastic restoring force of the elastic locking arm. Because of this, in the event that a strong unlocking force is exerted on the elastic locking arm that is being secured to be deflected and deformed, the locking of the distal locking portion and the locking projection is released. To cope with this, Patent Document 1 discloses a structure in which a rib that restricts the elastic locking arm from being elastically deflected and deformed (that is, an arm restricting rib) is provided in addition to the locking projection and the elastic locking arm. The arm restricting rib is disposed on a back side of the elastic locking arm that is locked to the locking projection, and hence, there is no such situation that the arm restricting rib interferes with the distal locking portion when the elastic locking arm moves in the fixing direction. On the other hand, in the event that the unlocking force is exerted on the elastic locking arm that is in the secured position, the arm restricting rib interferes with the elastic locking arm. This prevents the elastic locking arm from being displaced largely in the elastic deflecting direction. In this way, providing the arm restricting rib attempts to realize the fixing structure that is more difficult to be unfastened.